This invention relates to an apparatus for obtaining information on the interior of an object for use in a CT (computer tomography) apparatus, and more particularly to an apparatus for applying an electromagnetic wave such as a light beam, X-rays or gamma rays or an ultrasonic wave to an object under measurement, and detect the electromagnetic wave or the ultrasonic wave affected by the interior of the object, thereby to obtain information on the interior of the object.
In a conventional apparatus for obtaining information on the interior of an object such as an organism, an electromagnetic wave source located at a certain position outside the object applies an electromagnetic wave to the object, and the electromagnetic wave affected by the interior of the object is detected at plural locations. In this case, in addition to the straightly-propagating component of the electromagnetic wave, the components scattered by the object are also positively utilized so that the relationships between the electromagnetic waves thus detected are analyzed to perform an image reconstruction, thereby to obtain information on the interior of the object. Such a conventional apparatus is disclosed in detail in Japanese unexamined published patent application No. 124443/87.
In the case of an X-ray CT apparatus, only the straightly-propagating component of the X-rays in the interior of the object under measurement is detected. In this case, the X-ray irradiating position and the X-ray detecting position are not important factors in the image reconstruction.
On the other hand, for the above-described conventional apparatus for obtaining information on the interior of an object in which the scattered components of the electromagnetic wave are positively utilized, the positions of an electromagnetic wave irradiating point and a number of electromagnetic wave detecting points are essential for the image reconstruction because boundary conditions for the image reconstruction cannot be determined if those positions are unknown and it is difficult to form a CT image. In the case where the object is an organism, no suitable means is available for detecting the positions of the electromagnetic wave irradiating position and the electromagnetic wave detecting positions because the organism is generally intricate in configuration and not rigid.